1. Field of the Invention
This invention relates generally to a solid state color camera, and is directed more particularly to a solid state color camera which employs as its solid state image sensing device a semiconductor body such as a charge coupled device (CCD) chip, a bucket brigade device (BBD) or the like.
2. Description of the Prior Art
In the art there is proposed such a solid state color camera using a CCD ship which takes an interline transfer system in the transfer systems for carriers produced in response to an object to be picked up. The CCD chip in the form of the above carrier transfer system generally has one vertical shift register for each of a plurality of image sensing elements which are arranged in the vertical direction. The carriers from the respective vertical shift registers are fed to a horizontal shift register by 1H (H is one horizontal scanning line) and the information of 1H is read out from the output terminal of the horizontal shift register. The frequency of a clock pulse P.sub.H applied to the horizontal shift register is selected generally as 4.5 MH.sub.z or more. If, however, the frequency of the clock pulse P.sub.H is selected to be the color subcarrier frequency of the standard color television signal of the NTSC system, since there is no need to convert the clock frequency to the color subcarrier frequency, a signal process circuit for converting an output signal of the camera to a signal of the NTSC system becomes simple. The above is described in the U.S. application, Ser. No. 794,804, whose assignee is the same as that of the present application and which was filed May 9, 1977. If, however, the clock frequency is selected to be the same as the color sub-carrier frequency, the following problem appears. It is well known in the NTSC system, the phase of the color subcarrier frequency f.sub.S returns to the original one at every four fields. If the arrangement pitch of image sensing elements in a CCD chip in the horizontal direction is selected as .tau..sub.H, there occurs in such a case, depending upon the phase relation of the image sensing elements and the color sub-carrier frequency f.sub.S, no signal reading can be achieved from a vertical shift register in which no image sensing element exists. Thus, it becomes necessary that the signals corresponding to the image sensing elements on the vertical shift register be such signals as are provided by shifting signals from image sensing elements on the left and right sides of the vertical shift retister by a time corresponding to 1/2.tau..sub.H. To this end, if the signal is read out in the order of the phase of the color sub-carrier frequency, it is necessary to provide a phase adjusting circuit and hence it is also necessary to provide a switching signal generator circuit which produces a switching signal for the phase adjustment. As a result, the whole circuit construction becomes complicated and it becomes meaningless to select a clock frequency which is the same as the color sub-carrier frequency.
Further, even if the phase is corrected and the normal phase is obtained, since the inherent picture element is shifted by 1/2.tau..sub.H, the positional movement or shift of the image can not be corrected.